Using immuno-PET imaging to monitor kinetics of T cell-mediated inflammation and treatment efficiency in a humanized mouse model for GvHD

Abstract

Purpose Hematopoietic stem cell transplantation is the only curative treatment for several hematological malignancies and immune deficiency syndromes. Nevertheless, the development of graft-versus-host disease (GvHD) after transplantation is a severe complication with high morbidity and mortality. The aim of this study was to image human T cells during GvHD development and their migration into GvHD-related organs. By using a radiolabeled anti-human CD3 monoclonal antibody (mAb), we were able to visualize GvHD progression in a humanized mouse model. Methods Human peripheral blood mononuclear cells (PBMC) were transferred into immunodeficient mice (initially n \u2009=\u200911 mice/group) to induce GvHD. One group additionally received regulatory T cells (Treg) for prevention of GvHD. T cell migration was visualized by sequential small animal PET/MRI using 89 Zr-labeled anti-human CD3 mAb. Flow cytometry and immunohistochemistry were used to measure T cell frequencies in relevant organs at different time points after engraftment. Results Using radiolabeled anti-CD3 mAb, we successfully visualized human T cells in inflamed organs of mice by 89 Zr-anti-CD3-PET/MRI. Upon GvHD progression, we observed increased numbers of CD3 + T cells in the liver (22.9% on day 3; 94.2% on day 10) and the spleen (4.4% on day 3; 58.8% on day 10) which correlated with clinical symptoms. The liver showed distinct spot-like lesions representing a strong focal accumulation of T cells. Administration of Treg prior GvHD induction reduced T cell accumulation in the liver from 857\u2009±\u2009177 CD3 + cells/mm 2 to 261\u2009±\u200982 CD3 + cells/mm 2 and thus prevented GvHD. Conclusion 89 Zr-labeled anti-human CD3 mAb can be used as a proof of concept to detect the exact spatio-temporal distribution of GvHD-mediating T cells. In the future, radiolabeled T cell-specific mAb could be employed as a predictive early biomarker during the course of GvHD maybe even before clinical signs of the disease become evident. Furthermore, monitoring T cell migration and proliferation might improve tailored GvHD therapy.